This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The overall objective of this study is to investigate therapeutic efficacy of our gene delivery systems in mouse hindlimb ischemic model. We have successfully demonstrated an efficient in vivo gene (DNA or siRNA) delivery using biocompatible polymers (poly [unreadable]-amino ester for DNA delivery) and lipids (lipidoid for siRNA delivery) developed in Langer group. We are planning to investigate the in vivo feasibility of our gene delivery systems for treatment of cardiovascular diseases. 1. The first specific aim is to treat hindlimb ischemia with a lipid-mediated injection of siRNA for apoptotic molecules (e.g. SHP-1). Silencing of pro-apoptotic factors which are highly expressed in ischemic tissues could reduce cell apoptosis caused by no blood flow in ischemic tissues by blocking apoptotic signal pathway in the cells in ischemic regions, which may prevent limb muscle degeneration after ischemic event. 2. The second specific aim is to treat hindlimb ischemia with a polymer-mediated injection of angiogenic factor DNA (e.g. VEGF). Delivery of DNA for angiogenic factors could enhance angiogenesis process in ischemic limb muscle. However, our previous study showed that local injection of reporter DNA (luciferase) using the polymeric vectors into limb muscle did not show significant reporter protein expression in muscle tissues (Anderson et al., Proc Natl Acad Sci USA 2004;101:16028-16033). Thus, we are also considering the local injection of human endothelial cells or human mesenchymal stem cells in vitro genetically modified with VEGF DNA using our polymer-based delivery system as an alternative strategy for therapeutic angiogenesis.